This invention is directed to plastic construction materials having enhanced fire retarding properties. More particularly, this invention is directed to plastic construction materials containing a fire retarding quantity of the oxidation product of certain asphalts.
Plastic construction materials, as used herein, due to their varied and desirable properties, find utility in a wide array of employments. Thus, some plastic construction materials are used as thermal and electrical insulators, while others are used to make construction materials and furniture, and still others, such as petroleum asphalts, which are colloidally dispersed hydrocarbons in crude petroleum and can be obtained by fractionation of source petroleum, or bitumens, are used to make road and roofing compositions. In their final forms, plastic construction materials can be made into rigid bodies and flexible bodies, foams and solids, etc. The variety of physical properties of plastics has permitted them to become used in an extremely broad spectrum of applications. One common fault with plastics, however, is the fact that plastics, in fact, most polymers, are organic in nature and, thus, tend to burn or decompose when exposed to heat and oxygen.
The term "plastic construction materials", as used herein, is meant to encompass a wide variety of materials which can generally be described as being composed predominantly of an organic substance of large molecular mass, which is solid (or at least semi-solid) in its finished state, at standard temperature and pressure, but at some point in its manufacture or processing can be shaped by flow. Typically, many, but not all, of such materials are polymeric and are usually thermoplastic or thermosetting. These materials can be molded, cast, extruded, drawn, coated onto a substrate or laminated into various shapes and objects such as, beads, powders, films, fibers, plates, filaments or rods.
Bitumens are a class of amorphous, solid, semi-solid or viscous, cementitious substances, natural or manufactured, composed generally without limitation of high molecular weight hydrocarbons, as typically found in asphalts, tars, pitches and asphaltites. Bituminous materials are typically derived from asphalt or coal tar, with asphalt found naturally or attainable as a by-product of crude oil refining, and coal tar and pitches produced by the destructive distillation of coal. The compositional make up of coal, coal tar pitches, crude oils and natural asphalts vary depending upon the geological origin and/or geographical source. As a result, the physical characteristics of any one bituminous material, whether natural or manufactured, can differ markedly from another. The variety of bitumens give it wide utility in the building and construction industry.
The performance required of any such bituminous material is determined by its end use and/or application and is gauged by one or more measurable properties. A bitumen used in the fabrication of a roofing product can be defined by its softening point, penetration, flash point, viscosity-temperature relationship, among other such performance properties.
For illustrative purposes, consider asphalt as a representative bitumen used for building/construction. Asphalt materials used in the roofing context must be designed to perform several somewhat diverse functions. In order to saturate and impregnate an organic or comparable base material, a roofing asphalt must be very fluid at processing temperatures. In addition to saturation, the asphalt must also serve as a medium for various fillers and/or stabilizers, and promote surface adherence of mineral granules. Once applied as part of a roofing material, the asphalt should retain its durability and/or weather resistance over a wide range of temperature extremes. Evaluation of its performance properties determines the suitability of any one asphalt for a given roofing application.
The overall performance of a roofing composition will depend upon the properties of the various components, as well as their interaction and interdependence upon one another. For example and as mentioned above, coating asphalts are often reinforced with a mineral stabilizer/filler such as ground limestone, slate, or traprock. The stabilizer/filler enhances asphalt durability and increases resistance to fire and weathering. Depending upon the specific physical and/or performance requirements, such asphalt materials can be incorporated into any one of a number of residential and commercial roofing products, including shingles, roll roofing, underlayments and various membranes.
Where a bituminous material is intended for a roofing or other application does not initially have the desired performance properties, further processing can modify and/or tailor the bitumen for a given use/application. Using asphalt as an example, refining processes can be altered to provide the desired asphalt. Another approach is to incorporate the bitumen into a cold-applied system, which can take the form of one of various cutback solvent and aqueous emulsion compositions.
A common modification technique is oxidation of the bitumen through the introduction of hot air through a heated fluid bitumen. While the mechanism is not fully understood, the heat and oxygen are thought to initiate various chemical reactions, changing the physical properties of the bitumen. This "air blowing" process can be monitored and halted when the desired properties/characteristics are obtained. Other methods, including addition of various catalytic agents, can also be used to effect oxidation, modify the bitumen material and alter its performance properties.
The addition of modifiers has been used to overcome many problems. For over 100 years, natural rubber has been incorporated into bitumens (often emulsified, cutback or otherwise treated) to provide elasticity and improve the handling and service qualities. More recently, synthetic or reclaimed rubber, alone or with other modifiers, such as, fibers, fillers, natural asphaltites, oils, and other polymers, have been incorporated into asphalt to modify various physical properties relating to viscosity or flow, extendibility, and brittleness. Numerous polymeric systems have been used to modify bitumens.
As known to those skilled in the art the terms bitumen and bituminous can refer generically to various asphalts, coal tars, pitches and the like. However as it is also understood that outside North America and, particularly, the United States, the term "bitumen" is applied generically to mean other asphalt materials. The compositions of this invention include those comprising the high molecular weight hydrocarbons which predominate and are found in asphalts, coal tars, pitches, asphaltites and the like, notwithstanding any difference in generic nomenclature. Accordingly, the bitumen component of the inventive compositions described herein can be drawn, without limitation, from various known sources of asphalt, coal, tar, and coal tar pitches, whether neat, dissolved, emulsified, or polymer modified.
More specifically, an asphalt material treated in accordance with this invention can be derived from any one of a number of refined crude oils, naturally occurring asphalts, and combinations thereof. Included within the broad category of refined crude oils are various recycled asphaltic waste materials. More particularly, the asphalt material can be a roofing asphalt having physical properties meeting or equivalent to ASTM D 312 standard specifications for use of such an asphalt in built-up roof construction or an asphalt having physical properties meeting or equivalent to ASTM D 449 standard specifications for use in damp-and waterproofing. While various physical properties are described in the context of recognized ASTM standards, comparable and/or equivalent standards and specifications can also be used to describe this bitumen component, including but not limited to such standards recognized in Germany, the United Kingdom, Italy and Canada.
It should be understood and as is apparent from the examples, tables and surveys which follow that the asphalt element/component of method(s) and/or compositions of this invention is not limited to any one type or grade specified in the latest revision of the aforementioned ASTM standards and/or any previous version thereof. Preferred embodiments include specified types and/or grades where improved performance properties are desired, and the modifications/enhancements contemplated herein include those associated with movement from one type or grade to another and depending upon use or application. With equal utility, the bituminous compositions can comprise non-air blown or partially air blown asphalts having physical properties either within or outside the ASTM standards. As referenced in each of the aforementioned ASTM standards, incorporated herein in their entirety, and as well-known to those skilled in the art, the bitumen specified under each standard is prepared from commercially-available raw materials by known methods. The same can be used with the present invention, with the resulting compositions suitable for air blowing or having the physical properties of a specific ASTM type or grade.
Over the course of the years, many suggestions have been made to reduce the flammability, ignition, combustion or flame spread of various plastic construction materials (including petroleum asphalts used in building construction). Thus, for example, it has been proposed to employ a variety of phosphorus compounds (e.g., polyphosphates and salts of phosphoric acid) as a means of imparting fire retardancy to many materials. See for example, U.S. Pat. Nos. 3,513,114; 4,058,643; 5,198,483; and 5,225,464. It has also been proposed, for example in U.S. Pat. No. 4,365,026 and 3,654,190, to employ halogen, particularly bromine, compounds as fire retardants. Suggestions have been made to employ coal fly ash, as an inert material, to increase the fire retardancy of materials, such as in U.S. Pat. Nos. 4,425,440; 4,229,329; 4,331,726; 4,659,385; and 4,430,108. Melamine has been proposed, especially for use with polyurethane, in U.S. Pat. Nos. 4,385,131; 4,757,093; and 3,654,190. Other materials, such as alumina trihydrate (U.S. Pat. No. 4,871,477), sodium silicate (U.S. Pat. No. 4,956,217), and antimony pentoxide (U.S. Pat. No. 5,154,970) have also been proposed for use as fire retardants. The art also teaches that various of these materials can be incorporated into the material to be protected or applied as a coating or paint. It has also been proposed to employ many of these materials as well as ammonium sulfate and silicone polymers to enhance the fire retardancy of asphalts for use in construction applications (U.S. Pat. No. 5,102,463).
All of the above mentioned materials impart fire retardant properties to a greater or lesser extent depending upon the fire retardant chemicals themselves and the compositions with which they are employed. Futhermore, while not all fire retardants are equally useful in all materials, it has been found that a fire retardant demonstrated to have utility in one type of material will generally have fire retardant capability in species of the particular type of material. Similarly, it is also known that if a fire retardant has utility in connection with a group of materials, another fire retardant having utility in one of the groups will also have utility in the other members of the same group. The outline of this can be seen in the following table developed from The Chemistry and Uses of Fire Retardants, John W. Lyons, Wiley-Interscience, 1970 and Handbook of Flame Retardant Chemicals and Fire Testing Services, Technomic Publishing Company, Inc., 1992.
__________________________________________________________________________ Phosphoric Halogen acid, salts, Phosphorous (Chlorine/ Alumina and esters oxides Antimony Boron (Bromine) Trihydrate __________________________________________________________________________ Cellulose X X X X X X Polyolefins X X X Vinyls X X X X Acrylics X X X X Polystyrene X X ABS X X X X Rubber & X X X X X elastomers Asphalt X X X X X Engineering X X X X Plastics Polyurethane X X X X Epoxy X X X X X __________________________________________________________________________
The cost for obtaining a particular degree of fire retardancy also varies depending upon the cost of the particular fire retardant chemical and the quantity in which it must be employed to provide the desired degree of fire retardancy. Accordingly, there is a continuing demand for new and different materials that will impart or enhance fire retarding properties of materials, generally, but particularly in connection with plastic construction materials, as defined above.